History: In the late 1880s, Architect/Engineer
Gustave Falconnier [1845-1913] of
Nyon, Switzerland, invented a novel
type of glass building block or "glass brick" (German
glasbaustein or glassteine,
French brique de verre).
Falconnier's bricks were
blown in a mold
(BIM) like bottles, but had the original feature of being sealed air-tight
with a pastille of molten glass while hot (see right); after cooling, the
hot air trapped inside contracts, forming a partial vacuum.

The other early type of glass brick, made by Deutsche Luxfer
Prismen-Gesellschaft, Deubener Glaswerke and Siemens (these last two very
similar, see above) were unsealed and shaped (and sized) like traditional
masonry bricks, but lacked a bottom surface. They had problems with
condensation and dust collection on their interior surfaces, which could
never be cleaned.

"By making such bricks or blocks hollow, especially when they are
made air-tight, they possess several advantages over other materials,
being cheap, light, durable, and ornamental. Further, by reason of
their inclosing and confining air in a state of rest they serve as
non-conductors of heat."
—US Patent No. 402,073

Falconnier's briques were manufactured by Albert Gerrer of Mulhouse
(Haut-Rhin), S. Reich & Co. of Vienna and others. Their sides were
recessed to take mortar and they were laid up like ordinary masonry bricks,
with or without embedded metal reinforcing.

Haywards Ltd. bought the patent and marketed
them in England for vault and window walls. Despite initial interest
from important period architects such as
Hector Guimard,
Auguste Perret and
Le Corbusier, and some
prominent installations
(La Mission d'Algérie,
house of Mumm,
etc), Falconnier's design was apparently not a great commercial success. The
bricks are rare today, and existing installations even rarer. They suffered
from the same defect as early vault lights: damaged glass could not easily be
replaced. Falconnier briques are sometimes mistaken for fishing net floats.

Partial bricks: For finishing square openings,
each pattern was also made in ¾, ½
and ¼ sizes. A ¾ brick finished the long side, a ½
brick finished the short side, and a ¼ brick finished a corner.

Markings: Falconnier bricks are embossed
a number of different ways; here are a few: (// separates panels,
/ separates lines on same panel)

Usually "FALCONNIER // DEP FRANCE /
BELGIQUE +n" where n is the style#.

"FALCONNIER // 5" (on a light
aqua #6 brick). Seal: "FALCONNIER / DR 10708". I don't know what
the 5 refers to, but this is the flat-faced varation of the #6, so
maybe the #5 is just not shown in the catalog.

"FALCONNIER // No 9. ¼ //
DLERHÜTTEN / PENZIG" on a clear #9¼-brick.
Note, the 'A' from ADLERHÜTTEN is missing due to lack of
room and the N is cramped; who planned that?

Just "GLASSHÜTTE GERRESHEIM"
on a light aqua #9; the seal is unmarked.

Colors: Most bricks were light aqua, the usual
color of glass made from sand with iron contamination (which is most sands,
as any child who's played in a sandbox with a magnet can attest), but other
colors were available at extra cost:
clear for improved light transmission, and
decorative colors amber, green, blue and
(opal) milkglass (all colored in the mass). A red brick was made by casing
a clear brick in a thin layer of expensive, gold-based ruby glass. The
patent mentions coloring "either in the mass or by coating or covering
them inside or outside in full or in part with layers of metal or paint",
Additional ornamentation by sand-blasting, cutting and engraving, or acid
etching is also mentioned, but I have yet to see these variations.

Value: Despite rarity, prices are low since
there are very few collectors of early glass bricks (basically, me),
so there is little demand. The most common brick, a #8 in light aqua, is
difficult to sell at any price. I have seen hundreds for sale (often in
large lots), and would price them at about US$5 in quantity, more singly.
Rarer patterns, colors, and partial bricks are all worth more. The high
end is about US$150.

Finis: Modern-style two-part fused glass
blocks were perfected in the 1930s, more than forty years after Falconnier's
bricks were introduced. Around the same time, Belgian company
Etablissements Gaston Blanpain-Massonet of Bruxelles was still
producing bricks in the #8 pattern (always the most popular) as seen in
this catalog page, as well as the glass bricks
of style Glasfabriek Leerdam.

Four basic shapes were produced: square (No. 6, in two variations), a lozenge
or watch-with-band shape (No. 8), squashed hexagon (No. 9), and four
variations of a regular hexagon (Nos. 7, 7½, 10 and 11). All
tessellate, forming
a repeating pattern that completely fills a space. No. 8 was the most
popular shape and so is the most common now, followed by No. 9 (also
fairly common), then regular hexagon and square, which are rare;
I estimate the ratio at about 100:50:5:1.